With development of information era and acceleration of rhythm of life, a touch technology has gradually replaced traditional mouse and keyboard for the characteristics thereof, such as humanized designs, simple and rapid input, and the like, and has been widely applied to various electronic products, wherein a capacitive touch screen has been widely used for its advantages, such as a rapid reaction speed, high sensitivity, good reliability, high durability and the like.
According to different modes of setting a touch sensing layer in a display panel, a touch display panel is classified into structures, such as Add on Mode, In-cell and On-cell, etc. An Add on Mode touch display panel cannot satisfy ultra-thin requirements for some hand-held devices and portable devices because of a touch screen and a display panel being disposed independently of each other and the thickness of the product being relatively large. An In-cell touch display panel is disposed by integrating a touch sensing layer into an inner side of a color filter (CF) substrate of a display panel, but the production yield of the In-cell touch display panel is comparatively low due to the comparatively complicated structure and preparation process. An On-cell touch display panel is disposed by setting a touch sensing electrode on an outer side of a color filter substrate of a display panel, and is also one of current main stream touch structures. Generally, the On-cell touch sensing electrode is embed-disposed between a color filter substrate and an upper polarizer.
At present, during the preparing process of the On-cell touch display panel, a liquid crystal panel is first generally formed and includes an array substrate and a color filter substrate which are disposed to face each other, a liquid crystal layer being disposed between the array substrate and the color filter substrate; then a layer of ITO thin film is deposited on the color filter substrate of the liquid crystal panel and is etched to form a patterned touch sensing electrode. The crystalline ITO thin film has characteristics of lower impedance and higher transmissivity than the noncrystalline ITO thin film, thus, the ITO thin film for forming a touch sensing electrode is preferably a crystalline ITO thin film.
The existing method of forming a crystalline ITO thin film is mainly a high temperature annealing crystallization method: 1. depositing a noncrystalline ITO thin film using a low temperature sputtering process; and 2. placing the noncrystalline ITO thin film in an annealing furnace to perform a high temperature annealing crystallization process to obtain a crystalline ITO thin film. However, when forming a crystalline ITO thin film on a liquid crystal panel, since the highest temperature which a liquid crystal layer in a liquid crystal panel may bear is lower than 140° C., while the crystallization temperature of the noncrystalline ITO thin film is generally higher than 200° C., a traditional high temperature annealing crystallization method cannot be applied to forming a crystalline ITO thin film on a liquid crystal panel.
Hence, how to form a crystalline ITO thin film on a liquid crystal panel is a problem which the industry is exploring and solving all the time.